Pressure responsive power element



Aug. 16, 1960 G. ASAKAWA ETAL PRESSURE RESPONSIVE POWER ELEMENT FiledJune 2, 1955 m m #0 w 3 MM V E SE INMW [m 4 Gr 41% H; M T R 65 M G3 5 vB United States Patent George Asakawa and Sergius Vernet, YellowSprings,

Ohio, assignors to Antioch College, Yellow Springs, Ohio, an Ohiocorporation Filed June 2, 1955, Ser. No. 512,707

2 Claims. (Cl. 137-789) This invention relates to a pressure responsivepower element.

Power elements of the type with which we are concerned generallycomprise a vessel in which is contained or into which is introduced thepressure-producing medium. This pressure-producing medium may be amaterial responsive on temperature increase to expand and exert apressure, as for example, material 16 disclosed in United States PatentNo. 2,534,497, issued on December 19, 1950, to John C. Albright. Thepressure-producing medium may also be a material introduced into thevessel under pressure, as in the Fig. 3 arrangement of theabove-identified Albright patent.

The pressures produced by the pressure-producing medium are transmittedthrough a diaphragm to a body or plug of pressure-transmitting materialpositioned within a cover-like housing overlying the diaphragm. A

piston is slidably positioned in the cover-like housing and is springurged into the housing interior in opposition to the action of thepressure-producing medium. Pressure decrease in the pressure-producingmedium allows the spring to move the piston into the housing, and 1pressure increase in said medium moves said piston out of the housing.

It is desirable that the piston move immediately in response to pressurechange within the pressure-producing medium. It is accordingly necessarythat the pressure-transmitting plug be of an incompressible pliablematerial and be so housed in the power element as to at all times occupythe full space between the piston and diaphragm, thereby precluding anylost motion between the pressure-producing medium and piston.

It is also desirable that after successive pressure change cycles thepiston return to its same position in the housing. It is accordinglynecessary that no flow of material take place into or out of the powerelement interior, as such flow of material would vary the returnedposition of the piston.

It is further desirable that each successive pressure change cycle beaccompanied by the same total piston travel. It is accordingly necessarythat none of the pressure-producing medium escape from within the powerelement, as such escape would reduce the total piston travel.

It is further desirable that the power element retain the abovediscussed characteristics over a relatively large number of pressurechange cycles. It is accordingly necessary that the diaphragm berelatively free from ruptureproducing forces during flexure (as onpressure change of the pressure-producing medium). Suchrupture-producing forces occur when the diaphragm is caused to stretch.It is accordingly desirable to avoid stretching the diaphragm.

One object of the present invention is to provide a power elementcomprising a pressure-producing medium and piston, wherein the pistonmoves immediately in response to pressure change within thepressure-producing medium.

Another object is to provide a power element wherein no material isallowed to flow into or out of the power element interior.

Another object is to provide a pressure responsive power elementcomprising a piston, wherein the piston returns to its same positionafter successive pressure change cycles.

Another object is to provide a power element comprising apressure-producing medium and diaphragm, wherein none of thepressure-producing medium is allowed to escape from within the powerelement.

Another object is to provide a power element comprising apressure-producing medium and piston, wherein successive pressure changecycles are accompanied by the same piston travels.

Another object is to provide a power element which will retain a usefuloperative life over a large number of pressure change cycles.

Another object is to provide a power element including a flexiblediaphragm, wherein the diaphragm is relatively free fromrupture-producing forces during flexure.

Another object is to provide a diaphragm which flexes withoutstretching.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein likereference charactersdesignate corresponding parts in the several views.

In the drawings:

Fig. 1 is an elevational view of one embodiment of the invention,

Fig. 2 is a sectional view taken on line 22 in Fig. l, and

Fig. 3 is an elevational view of a pressure-transmitting plug employedin the Fig. 2 embodiment.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings,

since the invention is capable of other embodiments and of beingpracticed or carried out iri various ways. Also, it is to be understoodthat the phraseology or terminology employed herein is for the purposeof description and not of limitation.

The power element is generally designated by reference numeral 1 andincludes a cylindrical cup or vessel 2. A pressure-producing medium '3is contained in or introduced into cup 2.

The power element may be employed as a thermostat or as a pressurestat.When the power element is employed as a thermostat medium 3 is containedin cup 2 and includes a thermally expansible material, as for examplethe material disclosed in United States Patent No. 2,259,846. When thepower element is employed as a pressurestat cup 2 is provided with aconduit 4 and medium 3 is a material introduced into cup 2 underpressure through conduit 4.

Cup 2 is provided at its mouth with a flange 5, and sealingly seated onthis flange is a concavo-convex diaphragm 6 of flexible material,preferably vulcanized rubger. The central portion 7 of diaphragm 6 isthickene A cover-like housing 15 overlies diaphragm 6 and is provided'with a sleeve-like extension 8. An opening 9 18 provided in extension 8and a piston 11 is slidably positioned in this opening. Against an innersurface of extension 8 there is positioned an anti-extrusion washer 12,and in an elongated bore 17 formed in extension 8 there is positioned aplug-like body of pressure-transmitting material 13. Washer 12 wipinglyengages the wall of piston 11 and prevents any of material 13 from beingcarried out with the piston, although material 13 is preferably of anon-sticking character so as to aid in preventing carry out of material.Material 13 is preferably the same, solid, cohesive, non-sticking,reshapeable material as that disclosed in United States-patentapplication, Serial No. 498,655,-now Patent 2,906,123, filed on April 1,1955. As disclosed therein the material comprises discrete solidresinous particles (as for ex ample polytetrafluoroethylene) dispersedin and coated by a flowable binder (as for example polyhutene). Theflowable binder separates the resinous particles so as to prevent themfrom sintering together into a rigid mass. Material 13 thus has theadvantage of easy reshapa bility for eflicient pressure transmission, aswell as non-fluidity for minimum leakage. Prior to its insertion intothe interior of extension 8 material 13 takes the cylindrical shapeshown in Fig. 3. A spring (not shown) urges piston 11 into the interiorof the power element and forces material 13 to conform to the wallsurfaces of extension 8, piston 11 and diaphragm 6.

In the case where material 3 includes a thermally expansible material,assembly of the power element is effected by first positioning a body orpellet of medium 3 in cup 2. The pellet is formed with a depression 14-and diaphragm 6 is seated on flange 5 so as to have its convex surfaceconform to the contour of depression 14. Washer 12 and plug 13 arepositioned within housing 15, and a ring 16 is employed to clampinglyretain housing 15 and cup 2 in their Fig. 2 positions. Piston 11 isinserted into housing 15 and releasably urged therein by theaforementioned spring. Spring-urging of piston 11 into housing 15 causesmaterial 13 to exert a pressure against diaphragm 6 so as ot compressportion 7 against the surface of depression 14.

Operation of the power element is such that on pressure increase ofmaterial 3 diaphragm 6 is flexed upwardly, and 'material 13 is caused tosqueeze or push piston 11 outwardly against the action of its spring.Pressure decrease of material 3 allows the spring to move piston 11downwardly to its Fig. 2 position.

Pressure change of material 3 is accompanied by flexing of diaphragm 6but without any stretching thereof. As a result the life of thediaphragm and power element are increased.

During both pressure increase and pressure decrease of material 3pliable material 13 easily and immediately conforms to the changingpositions of piston 11 and diaphragm 6. As a result no void spaces areformed within the power element interior such as might allow forentrance of matter from the surrounding atmosphere.

Consequently there is no lost motion of the piston, and piston travelsare uniform over successive pressure change cycles.

Having thus described our invention, we claim:

1. A power element comprising a cup; pressureproducing material withinsaid cup; a concavo-convex diaphragm having its peripheral edge seatedon the rim of thecup and having its central portion depending into thecup interior; an annular housing having an annular face clampinglyseated on the diaphragm periphery and having an elongated tubularextension projecting axially away from the cup; an annular wallprojecting radially inward from theterminal end of the extension todefine an opening substantially smaller than the internal diameter ofsaid extension; a piston closely fitting the opening and slidablyextending therethrough to a point adjacent the diaphragm; a body ofsolid pliable, pressuretransmitting material surrounding the piston inthe space between the diaphragm and wall opening; saidpressuretrans-mitting material comprising discrete solid resinousparticles dispersed in and coated by a flowable binder so as to permitthe material to easily reshape itself in accordance with pressurechanges without tendency to return to its original shape; whereby, ondevelopment of increased pressures within the cup the diaphragm iscaused to flex in the direction of the housing so as to force the easilyreshapable pressure-transmitting material to squeeze against the pistonand drive it through the opening; the easily reshapable character of thepressure-transmitting material allowing it to efficiently transmit thepressures, and the solid character of the pressuretransmitting materialpreventing it from easily leaking through the wall opening; the annularportion of the pressure-transmitting material within the tubularextension being packed therein to act as a piston guide as well as aseal preventing the entrance of ambient media.

2. The combination of claim 1 wherein the pressuretransmitting materialhas a volume substantially equal to the internal volume of the tubularextension, thereby permitting said pressure-transmitting material to beinitially formed as a cylindrical block and inserted into the annularhousing prior to assembly with the piston.

References Cited in the tile of this patent UNITED STATES PATENTS2,208,149 Vernet July 16, 1940 2,400,091 Alfthan May 14, 1946 2,534,497Albright Dec. 19, 1950

